Gallium is an important element which is used in a CIGS-type thin film solar panel or light emitting diode (LED) etc.
Gallium is widely distributed in the earth's crust, but there is no ore which richly contains gallium. A Bayer process which will be explained below is general as an industrial manufacturing method.
As a method for obtaining gallium from a Bayer solution, for example, there is known a method of coprecipitating gallium and aluminum by blowing carbon dioxide into a Bayer solution to obtain a concentrate of gallium, dissolving this in a sodium hydroxide, and electrolyzing this to obtain metal gallium. Further, there is known a method of directly electrolyzing a Bayer solution by using a mercury electrode to obtain gallium as an amalgam.
For example, NPLT 1 discloses a method of directly electrodepositing gallium from a Bayer solution.
Further, for example, in a step of manufacturing Bauxite from an ore extracted from mines or manufacturing aluminum, zinc, tin, or another metal or compound from sphalerite or cassiterite etc., a byproduct which contains gallium is frequently generated. For this reason, collection of gallium using the above byproduct as a natural resource has been studied.
For example, a method of separation and concentration of the gallium which is contained in a stannic chloride is disclosed in PLT 1.
The method which is disclosed in PLT 1 is a wet process, therefore there is the disadvantage that a large amount of waste liquid is generated when a large amount of ore is processed.
Further, for example, a method of collecting metal gallium from an oxide which contains gallium by a dry process is disclosed in PLT 2.
PLT 3 proposes a technique of recovering gallium from waste which contains gallium.
The methods disclosed in PLTs 2 and 3 are dry processes, therefore have no demerit such as generation of a large amount of waste liquid as in the method disclosed in PLT 1. However, the method disclosed in PLT 2 tries to obtain gallium having a further higher purity from a mixture or compound which already has a considerably high gallium concentration and is quite different from the technique of the present invention for concentrating the gallium up to a certain concentration from an ore which contains a minute amount of gallium. In the method disclosed in PLT 3, chlorine is added as an element causing chlorination. Poisonous chlorine gas must be removed from exhaust gas, therefore there is a problem in terms of the apparatus.
Further, PLTs 4 and 5 disclose methods of generating highly concentrated gallium oxide from metal gallium.
It is expected that the supply of gallium become increasingly insufficient in the future, therefore it has been demanded to develop a technique for separating or concentrating gallium from a mixture which contains a minute amount of gallium such as an ore extracted from a mine or used electronic components. A similar situation exists for indium as well, therefore it has been demanded to develop a technique of separating or concentrating indium from a mixture which contains a minute amount of indium.
PLT 6 discloses a method and apparatus for treating radioactive waste which heat radioactive waste which contains a volatile radioactive substance to vaporize and separate the radioactive substance.
PLT 7 discloses a method of treatment of spent fuel which recovers uranium from spent fuel which contains uranium nitride as a principal ingredient in a form of a nitride.
PLT 8 discloses a method of vacuum melting a tellurium material to produce highly pure tellurium.
PLT 9 discloses a method for recovering valuable substances from scrap alloy by sublimating and collecting at least one type of metal element among the elements which are contained in scrap alloy as a metal oxide and separating this from the remaining metal elements.
PLT 10 discloses a method and apparatus for recovering germanium which brings a germanium-containing solid and hydrogen chloride into contact to generate germanium tetrachloride.